Road milling bits and bit holders, the design of which, when made in differing sizes, can also be used for trenching machines and mining machines, have benefitted greatly from what has been termed a quick change shank, found in the instant inventor's prior U.S. Pat. Nos. 6,371,567; 6,685,273 and 7,883,155. Additionally, the construction features of the forward end of the advanced bit design found in applicant's U.S. Pat. No. 6,739,327 has been cited in over 70 later issued patents. The Burkett U.S. Pat. No. 5,161,627 disclosed that one could mount a diamond coated insert in a one-piece bit/bit holder body. A similar structure with a diamond coated tip is found at the Sionett U.S. Pat. No. 4,944,559. These diamond coatings have heretofore been formed in a standard process that includes high temperature, high pressure forming of same on a tungsten carbide high impact substrate.
A later version of the present applicant's prior invention of a quick change shank such as found in the U.S. Pat. No. 6,371,567 patent is provided in combination with a diamond tip and found at the Hall et al U.S. Pat. No. 8,118,371.
With diamond coated tips of road milling machinery, it has been found that the working life of the tip has been greatly increased. As such, it is no longer necessary to provide changeable bits in bit holders. The operating life of bits and bit holders are such that they can be physically combined in a unitary structure.
A need has developed for a lower cost combination diamond coated tip and front portion, formerly used on a removable bit, with a quick change bit holder.